The present invention relates to the type of thermosetting resin composition that is used broadly in the field of electric and electronic appliances; and, more particularly, the invention relates to a solvent-free thermosetting resin composition, a process for producing the same, and a product thereof, that is required, from the viewpoint of workability, to be in a liquid form before curing.
The present invention relates to a liquid sealing material and paste bonding material for mounting semiconductors and to the conductive paste material that is used for connecting the layers of a printed wiring board, all of which are used broadly in the field of electronic appliances. The resins used for these materials are required to have a filling ability with a filler and metallic powder and an ability to impregnate into glass cloth.
The resin, after being cured, on the other hand, is required to have high-temperature mechanical properties, so that the resin can be used at a high temperature during the mounting of components or in operation. Conventionally, an epoxy resin composition, which is in a liquid form at room temperature (25xc2x0 C.), has been used broadly in this field, and a reactive diluent, such as phenyl-glycidyl-ether, is added to lower the viscosity of the varnish. Besides, for a curing agent, a liquid acid-anhydride type is used to lower the viscosity of the varnish. However, when a low molecular-weight component, such as butyl-glycidyl-ether or phenyl-glycidyl-ether, is used as the diluent, the material properties of the cured resin, particularly those at a high temperature, tend to deteriorate (xe2x80x9cNew Epoxy Resinxe2x80x9d written by Hiroshi Kakiuchi, Article 9, 1988).
When liquid acid-anhydride is used as the curing agent, the amount needed is the same as the epoxy, and its applications are limited in view of the material properties, curing ability and workability (xe2x80x9cHigher Performance of Epoxy Resin, and Mixing Technique, Evaluation, and Application of Curing Agent: Section 3xe2x80x9d written by Technical Information Association, 1997).
In addition, since an applicable epoxy resin is limited to a low molecular-weight alicyclic type epoxy resin, such as vinyl-cyclohexene-dioxide (25xc2x0 C., 7 cps) or alicyclic epoxy-carbonate (25xc2x0 C., 360 cps), restraints arise in the material properties in that an amine type curing agent cannot be used due to its reactivity, the cured resin is brittle, and so on.
For this reason, aromatic liquid epoxy resins of a bisphenol A or bisphenol F type or a phenol-novolak type, which have excellent mechanical properties, bonding ability and heat resistance after being cured, have been used. However, since these resins have high viscosity at around room temperature (25xc2x0 C.), lower viscosity is attained by using both an alicyclic type epoxy resin and a reactive diluent, or by using a liquid acid-anhydride type curing agent at the sacrifice of the material properties of the cured resin.
On the other hand, as methods of improving the mechanical properties of the resin at a high temperature, the Japanese Application Patent Laid-Open Publication No. Hei 8-100107 (1996) discloses a polycondensation of the resin by adding metallic alkoxide to an epoxy resin; Japanese Application Patent Laid-Open Publication No. Hei 9-216938 (1997) discloses polycondensation of the resin after swelling a metallic alkoxide in a phenol resin; and Japanese Application Patent Laid-open Publication No. Hei 9-291131 (1997) discloses condensation of the resin by a sol-gel method after adding metallic alkoxide into a polyurethane resin. However, since the curing reaction involves polycondensation in these methods, there arises a problem in that water is generated during the reaction and blistering is caused on the interface of the compound material. Besides, in these prior methods, no consideration is given to the prevention of blistering and cracking caused on the interface of the compound material by a change in the temperature.
The Japanese Application Patent Laid-Open Publication No. Hei 8-199045 (1996) discloses a method where, in order to reduce the generation of thermal stress, alkoxyl silane and water are added to the epoxy resin dissolved in an organic solvent; and, after the alkoxyl group in alkoxyl silane is hydrolyzed, the solvent is removed, and then the resin is heated to cure it and to dehydrate and condensate the hydroxyl group. However, since water is generated in the curing process, this method leads to deficiencies, such as creation of a void.
It is indicated in Japanese Application Patent Laid-open Publication No. Hei 5-291438 (1993), which relates to a semiconductor device in which the semiconductor is sealed using an epoxy resin composition comprising epoxy resin, a curing agent and a reaction product of silane, that the resin composition increases the bonding ability of the semiconductor device with the frame and the silicon chip, and increases the moisture resistance and the reliability of the semiconductor device. This method, however, does not refer to the preliminary reaction of the silane compound in the epoxy resin, nor to the lowered viscosity of the resin.
It is indicated in Japanese Application Patent Laid-open Publication No. Hei 11-209579 (1999), which relates to an epoxy resin composition for sealing, comprising epoxy resin, a curing agent and a reaction product of silane, and containing a silane compound that contains a mercaptyl group, that the bonding ability of the resin composition can be improved when the silane compound containing a mercaptyl group is first hydrolyzed and then reacted with the epoxy resin. However, the mixture of the silane compound containing a mercaptyl group is 0.001 to 5 % by weight, and the invention does not refer to the realization of a lower viscosity by forming organosilicon compound polycondensates having a degree of polycondensation of 2 or higher.
Conventionally, to lower the viscosity of liquid thermosetting resins, there have been several methods using a reactive diluent, a liquid acid-anhydride type curing agent, or an alicyclic low molecular-weight resin. These methods, however, have caused a problem in that the material properties of the cured resin need to be sacrificed.
It is an object of the present invention to provide a solvent-free thermosetting resin composition which has a low viscosity and gives a cured resin having intact material properties, especially intact high-temperature mechanical properties, a process for producing the resin composition, and a product obtained by applying the composition.
In order to achieve the above object, it is required to provide a diluting component which has a lower viscosity than the thermosetting resin used as the base material; and, by using which, the high-temperature mechanical properties of the whole resin after being cured is equal to or better than those of the cured thermosetting resin itself, which is used as the base material.
The present invention relates to a liquid solvent-free thermosetting resin composition that is in a liquid form at room temperature (25xc2x0 C.), comprising an epoxy resin and a product of the reaction of an organosilicon compound with water as a basis, and to a process for producing the resin composition. That is to say, the present invention proposes to heat a solution of epoxy resin mixed with a product of the hydrolysis of an organosilicon compound and water and to remove the water and alcohol, to be generated as a byproduct, by heating, so as to offer a thermosetting resin composition with a low viscosity that is in a liquid form at room temperature. After the above process, a curing agent is added and the resin composition is heated to obtained a cured resin. The cured resin exhibits high-temperature mechanical properties equal to or better than those obtained by adding the curing agent to the epoxy resin and heating it to cure it.
The above organosilicon compound and water, when heated in the epoxy resin (that is, in the presence of the epoxy (resin) react with each other and form a liquid oligomer. The liquid oligomer is very much compatible with the epoxy resin and functions as a reactive diluent. Thus, the viscosity of the thermosetting resin composition resulting from the above can be reduced tremendously, and lower thermal expansion or higher thermal conductivity can be added to the resin composition by adding a lot of inorganic filler, such as alumina and silica.
The resin composition of the present invention, suitable for the sealing and die bonding material of a semiconductor device, is capable of providing a highly reliable semiconductor device. Besides, the composition is excellent as a conductive paste, because a lot of metallic powders can be mixed, and applying the composition to the through-hole of a multi-layer printed wiring board makes it possible to improve the reliability of the connection. The present invention is also applicable to the insulation material used in a rotary machine and a transformer, in which material a solvent-free casting resin and an inorganic filler are mixed.
The above organosilicon compound in an oligomer form has a SiO2 skeleton that is stable in terms of the mechanical properties thereof, and has a functional group that reacts with a curing agent commonly used for the epoxy resin. For this reason, when the above thermosetting resin composition is heated to cure it, the organosilicon compound in an oligomer form and the epoxy resin react with each other through the aid of the curing agent, and a uniform cured resin is formed preferably at a level of size of 10 nanometer or less, or more preferably 3 nanometer or less. As a result, a cured resin with excellent high-temperature mechanical properties is obtained.
Besides, the cured resin of the resin composition of the present invention does not generate a void or a crack that leads to deficiencies because, in the heating process prior to adding the curing agent where the oligomer is generated, the water and alcohol to be generated as a byproduct have been removed.
A summary of the present invention is as follows:
[1] A solvent-free thermosetting resin composition which comprises an epoxy resin (a) and a product (b) of the reaction of an organosilicon compound, represented by the general formula (1) 
(where R is an organic group containing a functional group reactive with an epoxy resin by addition reaction; and R1 is a methyl or ethyl group), with water, the product (b) containing organosilicon compound polycondensates formed in the epoxy resin (a) and having a degree of polycondensation of 2 or higher, and which is in a liquid form at room temperature (25xc2x0 C.).
[2] A solvent-free thermosetting resin composition which comprises an epoxy resin (a), the product (b) and a curing agent (c) as essential components, and which is in a liquid form at room temperature (25xc2x0 C.).
[3] A process for producing a solvent-free thermosetting resin composition, which is in a liquid form at room temperature (25xc2x0 C.), where, under the existence of an epoxy resin, an organosilicon compound represented by the general formula (1) and water are reacted with each other by heating at 60 to 160xc2x0 C. for 1 to 10 hours, and then a curing agent (c) is added. In the above, it is preferred that the amount of water is 3 to 0.02 times the organosilicon compound by mole ratio.
[4] A semiconductor device in which, at least, part of the semiconductor is coated or sealed with a thermosetting resin material, where the thermosetting resin material comprises a solvent-free thermosetting resin composition, which comprises an epoxy resin (a), the product (b) and a curing agent (c) as essential components and which is in a liquid form at room temperature (25xc2x0 C.), and an inorganic filler as essential components.
[5] A semiconductor device in which a semiconductor chip and a lead frame are bonded together using a die bonding material containing a thermosetting resin material, where the thermosetting resin material comprises a solvent-free thermosetting resin composition, which comprises an epoxy resin (a), the product (b) and a curing agent (c) as essential components and which is in a liquid form at room temperature (25xc2x0 C.), and a metallic powder or inorganic filler as essential components.
[6] A semiconductor device in which the semiconductor and a wiring board are mounted using a thermosetting resin material, where the thermosetting resin material comprises a solvent-free thermosetting resin composition, which comprises an epoxy resin (a), the product (b) and a curing agent (c) as essential components and which is in a liquid form at room temperature (25xc2x0 C.), and a conductive metallic powder as essential components.
[7] A printed wiring board which, at least, has two or more wiring layers, which layers are made conductive to each other using a conductive material containing a thermosetting resin material, where the conductive material comprises a solvent-free thermosetting resin composition, which comprises an epoxy resin (a), the product (b) and a curing agent (c) as essential components and which is in a liquid form at room temperature (25xc2x0 C.), and a conductive metallic powder as essential components.
Since the thermosetting resin composition according to the present invention has a low viscosity before curing by heat, it is applicable to any thermosetting resin molding. Before a curing agent is added, a mixture of the epoxy resin, organosilicon compound and water are heated so as to remove the reaction byproducts, such as water and alcohol. For this reason, byproducts, such as water and alcohol, are rarely generated in the curing process; and, therefore, even when a compound material is produced together with a base material, such as a metal, ceramic or resin, neither blistering on the interface between the base material and the resin composition of the present invention, nor cracking and separation on a molding, are caused.
The process for producing the resin composition is characterized in that, under the existence of an epoxy resin, the afore-mentioned organosilicon compound and water are reacted with each other, and, more specifically, reacted by heating at 60 to 160xc2x0 C. for 1 to 10 hours. In this reaction, it is preferred that the amount of water is 3 to 0.02 times the organosilicon compound by mole ratio.
In addition, the reaction product of the organosilicon compound and water has a SiO2 skeleton that is stable in terms of the mechanical properties, and it has a functional group that reacts with a curing agent commonly used for the epoxy resin. Since the heated and cured resin of the thermosetting resin composition of the present invention is highly heat-resistive and experiences little change in its modulus of elasticity at a high temperature because of the above, thermal stress and cracking hardly occur. Since a high modulus of elasticity can be maintained even at a high temperature, deformation of the thermosetting resin material by a load due to an external force can be controlled.
The present invention is able to lower the melt viscosity during heating of a thermosetting resin composition that is in a solid form at room temperature.
There is no particular limitation to the epoxy resin, and any well-known ones are applicable. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, glycidyl-diamine type epoxy resin, alicyclic type epoxy resin are applicable.
As the curing agent for the epoxy resin, general well-known chemicals that are used normally can be employed. There are available, for example, carboxylic acid anhydride, Class 1, Class 2 or Class 3 amine compound, Class 4 ammonium salt, dicyan-diamide, boron trifluoride-amine complex, organic acid hydrazide, imidazole compound, onium salt compound, a compound having phenol, cresol or xylenol as the basic skeleton as well as a derivative thereof and a polycondensate thereof, and Thiokol compound, out of which any can be selected for the purpose and application.
In addition, a well-known curing accelerator, mold releasing agent, coupling agent, coloring agent, plasticizer, diluent, flexibility adding agent, various rubber materials, and a photosensitive material can be added for the purpose and application.
An example of the organosilicon compound represented by the general formula (1) in accordance with the present invention includes the organosilicon compounds having a polyaddition type functional group expressed by the following chemical formulas (2) to (11). 